*looks around... crosses fingers* Ok, I have tried to reply to this seven or eight times now. Every time as soon as I start typing something comes up and I have to leave. Here goes:

I think that truly good art is whatever inspires thought or simply inspires. Under this definition, good art is (as stated so many times above) in the eye of the beholder. A collection of random dots on a canvas may be a waste of time to one person, and a awe inspiring image to another. I think the fact that something like 4'33" generated so much discussion as to what music is, in a way, solidified its claim of being art. I myself love it when an abstract painting catches me of guard and makes me wonder what was going through the artists head at the time he made it; putting myself in his shoes for a few seconds and seeing the world through his eyes. For me, that's what separates what I think is "good art" from what is not. Of course, the same work may be nothing more than a waste of space to the next person who comes along and vise versa.
I'm really happy to see the response this thread got. I figured I would get a lot of "meh" but I guess not.